Contact assembly means and method



Oct. 25, 1966 CROWLEY ETAL 3,281,763

CONTACT ASSEMBLY MEANS AND METHOD Filed April 24, 1964 2 Sheets-Sheet 1INVENTORS DAM\E.L QQSEPH CRcwLl-IY CHARLES Ream- SAuveRs aualdl,

Oct. 25, 1966 D, CROWLEY ETAL 3,281,763

CONTACT ASSEMBLY MEANS AND METHOD 2 Sheets-Sheet 2 Filed April 24, 1964NlCKEL.

PLATE GOLD PLATE FLUX ASSEMBLY UN FLOW TIN FAT STODDARD'S SOLVENT WASHINVENTORS DANIEL JOSEPH CROWLEY YCHARL as 'RoBER-r SANvs e B UnitedStates Patent 3,281,763 CONTACT ASSEMBLY MEANS AND METHOD Daniel JosephCrowley, Steelton, and Charles Robert Sanders, Harrisburg, Pa, assignorsto AMP Incorporated, Harrisburg, Pa.

Filed Apr. 24, 1964, Ser. No. 362,316 10 Claims. (Cl. 339-417) Thisinvention relates to an improved contact assembly and method ofmanufacture which features a new type of mechanical connection betweenassembly components to provide superior electrical and mechanicalcharacteristics.

In US. Patent 2,975,395 to G. C. Sitz, granted Mar. 14, 1961, there isdescribed a plugboard device of the type used to program electrical and/or electronic equipment. Part of the contact system of the plugboardassembly shown and described in the Sitz patent is formed of a stampedmetal spring member which carries a contact surface on a forward springportion and includes a support portion adapted to position and hold themember within an insulating board. This support portion further includesa receptacle adapted to receive a taper pin connected to a lead whichis, in turn, connected to equipment to be programmed by the plugboarddevice. The arrangement featured in the Sitz patent has proven to bequite adequate for standard uses and normal environment. In certainapplications, however, it has been found advisable to employ arelatively heavy solid metal seamless receptacle into which the taperpin member is plugged. Efforts were made to utilize the springconstruction shown in the Sitz patent in such uses with the solid metalreceptacle being inserted within the support portion and solderedthereto. A number of deficiencies with this construction developed. Oneof the principal problems appeared to be related to the incompatibilityof standard solder and solder-flowing methods with the base metal andplating material used for the contact spring. Another problem developeddue to the insertion and withdrawal forces required by the taper pinwhich caused displacement of the metal receptacle relative to thesupport portion and thereby mechanical and electrical failure of theassembly. The foregoing shortcomings were particularly objectionablebecause the failure most frequently arose after some period of use andwell after initial tests showed satisfactory mechanical orelectricalcharacteristics.

The foregoing problems led to the discovery upon which the presentinvention is based. As will become apparent from the descriptionhereinafter to follow, it is a general object of the invention toprovide a new and improved contact assembly wherein a relatively heavysolid metal member is mechanically and electrically joined to arelatively thin metal member and it is a particularobject to provide aplugboard contact spring assembly having a heavy metal taper pinreceptacle secured thereto in a manner to withstand the insertion andwithdrawal forces associated with taper pin techniques. It is a furtherobject of the invention to provide a novel method of manufacturing anassembly wherein a relatively heavy metal member is joined to arelatively thin metal member through the combined use of what might betermed soldering and crimping techniques. It is another object of theinvention to provide a method of joining metal members in a mannerproviding a low resistance stable electrical path with a soundmechanical connection. It is yet another object of the invention toprovide a novel means and method for connecting metal members which mustbe thereafter overplated with metals of different characteristics.

In the drawings:

FIGURE 1 shows the contact assembly of the invention in plan secured inan insulating board member sectioned 3,281,763 Patented Oct. 25, 1966for clarity and with a taper pin positioned relative to use with theassembly;

FIGURE 2 is an enlarged side view of the support portion of the contactassembly of the invention showing the taper pin receptacle securedtherein;

FIGURE 3 is an end view taken along the lines 3-3 of FIGURE 1;

FIGURE 4 is an enlarged side view of the contact assembly of theinvention showing the crimp employed therewith to lock the taper pinreceptacle within the assembly;

FIGURE 5 is a partial section taken along lines 5-5 of FIGURE 4 to showfurther details of the crimp employed with the invention; and

FIGURE 6 is a block-step diagram showing the method of the invention.

In FIGURE 1, the taper pin 10 is shown relative to insertion within thecontact assembly of the invention which is mounted in an insulatingboard 22. The taper pin 10 includes a forward contact portion 12 taperedalong its surface to engage and be wedged against a complementarysurface 42 within a taper pin receptacle 40 which is part of 20. The pinis connected to a lead 14 as by a crimp 16 through an insulating sleeve18. The lead 14, or many leads similar thereto, may be connected tocomponents of electrical and/or electronic equipment served by theplugboard which includes dozens or hundreds of contact assemblies, suchas 20. The assembly 20 carries a flexible contact spring 24 which isadapted to engage a pin member 25 extending from a movable board (notshown) of the plugboard assembly. The contact system formed by theseparts serves to make or break electrical paths through and between leadssuch as 14, the assembly 20, spring 24, pin 25, and an identical andsimilar combination of elements elsewhere in the plugboard. Referencemay be had to the aforementioned patent to Sitz for a generaldescription of plugboard systems.

The forces which the assembly 20 must carry in use include a transverseforce developed by reason of spring 24 being deflected by pin 25 and anaxial force along the center line due to the insertion and withdrawal oftaper pin 10. The assembly is locked against the transverse force byreason of the engagement of a support portion 26 with the aperturesurface 21 of board 22. The axial forces which tend to pull or pushassembly 20 out of the aperture are resisted by means of tabs, such as28, struck outwardly to engage the surface of board 22 as indicated, inconjunction with the inner transverse surfaces of spring members formedon the opposite end of the assembly.

The contact assembly 20 is initially inserted within board 22 by forcingthe end-carrying springs 30 into the aperture and forcing the assemblyalong the aperture until the tabs 28 engage the surface of the board.Thereafter, the springs 30 are formed outwardly to lock the assemblywithin the :board. In the embodiment shown, the assembly 20 is formed ofa fiat metal material, such as sheet brass, blanked, stamped and formedinto the configuration shown. The assembly support portion 26 isgenerally cylindrical and includes a seam 27, as shown in FIGURES 1 and3. At the end of 26, proximate springs 30, portions of the supportportion shown as 32 are formed inwardly to lock against the surface oftaper pin receptacle positioned generally within the support portion asbest shown in FIGURES 2 and 3. The portions 32 serve to orient 20 in thepanel through cooperation with a portion protruding into aperture 21 andto retain member 40 against rotational movement relative to the contactassembly 20 by means of engagement with a fiat 44 extending along thelength of the receptacle.

As can be seen from FIGURES 2 and 3, the exterior surface configurationof 40 is dimensioned to fit tightly Within the interior surfaceconfiguration of 20. In this regard, the seam 27 is utilized by anappropriate choice of dimensions to assure tight engagement of 20 and 40by providing a small space between the edges along the seam to permitthe receptacle to be wedged within 20 notwithstanding a slight oversize.The slots 31 and 33 are provided to permit the forming of portions 32inwardly to lock receptacle 40 Without affecting the portions 34 or thesprings 30.

The taper pin receptacle 40 is positioned in 20 with the taper boreforming surface 42 having its point of entry 46 as shown in FIGURE 2.The receptacle further includes the flat 44 above-mentioned and at theend opposite entry 46 an annular recess 48. It is through this recessthat receptacle 40 is locked against axial movement relative to 20 byreason of crimps or indentations formed in the wall of portion 26. Itwill be appreciated that relative movement between 20 and 40 would causea substantial increase in the resistance of the path through member 20.Relative movement between these two members could, but for the featuresto be explained, be occasioned by axial loads imparted during theinsertion or withdrawal of taper pin or by forces imparted by spring 24.

As an important part of the invention, the member 40 is looked throughthe provision of indentations shown as 50 and 52 in FIGURE 1 which serveto force the metal material of support portion 26 down within theannular recess 48 of member 40. FIGURES 4 and 5 show these indentationsin greater detail. From FIGURE 4, the indentation 52 can be seen to beformed of relatively straight sides 54, 56 which are spaced such thatthe width of the metal formed inwardly is substantially as wide as therecess 48. The body of metal is shown as 60 and is formed inwardly tocontact the bottom of recess 48 as indicated by number 58, FIGURE 5. Theconfiguration of the die which forms the indentation 52 can bevisualized from the dotted outline and from the resulting indentation.As should be apparent from FIGURES 4 and 5, this results in a shearingof the metal material .along sidewalls 54, 56 with a bending of themetal material as in 62 about a radius which is controlled to avoidcracking or splitting of the metal material.

In a preferred embodiment, the indentations 5t) and 52 are formed 180apart and the width, in an axial sense, is made to be slightly largerthan the width of the recess 48 such that the material of the bend 60 isvirtually wedged in compression down Within the recess and an abruptsurface is formed to hold against axial loading. This, in conjunctionwith portions 32, locks the receptacle 40 against rotational movement inaddition to locking against axial movement. As shown in FIGURE 2, and aswill be better described hereinafter, with respect to the method of theinvention, there is included between member and the member 40 a coatingof tin solder bonding the two members together to form a low-resistanceelectrical path therebetween. The flowing of the tin is accomplishedfollowing the crimping operation and both the crimping and flowing areaccomplished prior to any final plating operation.

The assembly, thus described, has been found to withstand axial loads of400 pounds and better with excellent electrical characteristicsmaintained through standard life tests. In an actual embodiment whereinthe assembly 21 was formed of brass stock of approximately 14thousandths of an inch in thickness and the axial depth of indentation52 was 20 thousandths of an inch. In this embodiment, the axial widthbetween surfaces 54 and 56 was 68 thousandths of an inch whereas thewidth of recess 48 was 63 thousandths of an inch to provide theabovementioned wedging action.

In manufacturing the assembly of the invention abovedescribed, thepreferred method is as indicated in the step-block diagram shown inFIGURE 6. The method contemplates prior to the first step that members40 and 20 are separated as indicated in FIGURE 6. The contact assembly20 is at this point unplated and uncrimped. The receptacle 40 is coatedwith tin along the portions of its exterior surface as indicated by theheavy line in FIGURES 2 and 3. It is preferred to prepare byscrew-machining a solid brass rod which has been previously tin plated.

With the contact spring 20 and receptacle 40 in the above-descrivedstates and cleaned, the receptacles are then fluxed, as for example, bybeing briefly submerged in a fiuxing solution such as 48 percent WWrosin and 52 percent denatured alcohol (by weight) and then permitted todry.

Next, the fluxed receptacle is inserted in the contact spring in therelative position shown in FIGURES 1 and 2 and crimped or indented inthe manner abovedescribed with respect to portion 32 and indentations52.

Thereafter, the assembly of 20 and 40 is then treated to achieve tinflow between the contact assembly by submerging in a preheated tankcontaining Hydrofol Tinfat No. at approximately 500 F.i10 F. for aperiod of five minutesione minute. This operation serves to flow the tinbetween the surfaces of 20 and 4t) and thus, solder the two piecestogether through the tin medium. Thereafter, the assembly is withdrawnfrom the Tinfat and dumped for cleaning in Stoddards solvent whichremoves excess Tinfat from the members.

Thereafter, a suitable plating such as gold over nickel may be appliedto the contact assembly in standard fashion.

The foregoing method has been found to provide an electrical connectionbetween the receptacle 40 and spring 20 which is superior to techniquesheretofore attempted. The method of crimping or indenting prior to thesoldering operation in conjunction with the particular type of solderingoperation has been found to substantially improve the mechanicalcharacteristics of the piece and assure long life in the presence ofadverse environments. The method has been found to be particularlycompatible with overplating after crimping and soldering.

Changes in construction will occur to those skilled in the art andvarious apparently different modifications and embodiments may be madewithout departing from the scope of the invention. The matter set forthin the foregoing description and accompanying drawings is offered by wayof illustration only. The actual scope of the invention is intended tobe define-d in the following claims when viewed in their properperspective against the prior art.

What is claimed is:

l. An electrical contact assembly including a barrel portion and acontact portion integral with said barrel portion, the said barrel andcontact portions being of relatively thin fiat metal stock of the typeadapted for ease of stamping and forming with the contact portion havingspring characteristics, a contact receptacle of relatively heavy metalstock secured in said barrel portion and adapted to receive a contactmember inserted therein, the receptacle having on a portion of the outersurface a thin layer of conductive material to electrically connect thereceptacle to the barrel portion, the receptacle further having a recessand being secured in said barrel portion and electrically connectedthereto by at least one indentation of the outer surface of said barrelportion forced into the recess of the said receptacle.

2. The assembly of claim 1 wherein the layer of conductive material is ametal having a relatively low melting point.

3. In a contact assembly of the type utilized in a plugboard, thecombination including a contact member formed of relatively thin metalstock having a mounting portion adapted to lock said member within aplugboard aperture and a forward spring portion which is resilientlyflexible to receive and be held in contact with a patch- Cofd pm underSubstantial pressure, the mounting portion including'at the opposite endto said spring an opening adapted to receive a taper pin member therein,a solid metal receptacle fitted within said mounting portion to receivesaid taper pin through said opening, said receptacle including in theoutside surface thereof a recess extending annularly at least aroundpart of said receptacle, the said mounting portion having a segmentformed inwardly into said recess to lock said receptacle againstrelative movement caused by forces developed during insertion andwithdrawal of the taper pin in said receptacle.

4. The assembly of claim 3 wherein the said mounting portion egmentformed inwardly into said recess includes at least one .wall sectiondefining a surface substantially perpendicular to the longitudinal axisof said receptacle and the said receptacle recess includes a surfacesubstantially perpendicular to the longitudinal axis of said receptacle,the said surfaces being in contact to lock against relative axialmovement.

5. The assembly of claim 3 wherein the said segment formed into thereceptacle recess includes two spaced surfaces substantiallyperpendicular to the longitudinal axis of the receptacle and said recessinclude complementary surfaces substantially perpendicular to thelongitudinal axis of the receptacle, the said surfaces of the segmentand recess acting to resist axial movement between receptacle andcontact member.

6. The assembly of claim 5 wherein the axial spacing of the recesssurfaces relative to the axial spacing between segment surfaces is suchthat the material of the segment is wedged under residual compression insaid recess.

7. An improved method for forming a mechanical and electrical connectionbetween a relatively heavy stock metal receptacle and the barrel portionof a contact member of relatively flat thin metal stock comprisingproviding a coating of metal material having a relatively lowmelting'point over a portion of the surface of the receptacle, placingsaid receptacle within said barrel portion, applying a crimp to saidbarrel portion to force the material thereof into engagement with saidreceptacle and heating said member and receptacle to a temperature andfor a period of time to flow the metal material between the receptacleand contact member.

8. The method of claim 7 wherein the method step of heating consists ofsubmerging the receptacle and contact member in a substantially neutraloil at a temperature of more than 375 9. The method of claim 8 whereinthere is a further step including submerging the assembly while heatedin a solvent to wash and remove the said oil.

10. In a contact assembly of the type utilized in a plugboard, thecombination including a contact member formed of relatively thin metalstock having a mounting portion adapted to lock said member within aplugboard and a forward spring member which is resiliently flexible toreceive and be held in contact with a. patchc-ord pin member, themounting portion including at the opposite end of said spring an openingadapted to receive a connector terminal, a metal receptacle fittedwithin said mounting portion to receive said terminal through saidopening, the said receptacle having a recess extending in annularfashion about a portion of its surface and including surfacessubstantially perpendicular to the longitudinal axis of the receptacleand spaced apart by a given distance, said mounting portion having twosegments spaced substantially apart and forced inwardly into saidrecess, the said segments having a width relative to the surfaces of therecess such as to be held under residual compression therein, theassembly further including extending between a substantial portion ofthe outside surface of the receptacle and a complementary inside surfaceof the mounting portion, a layer of conductive material fused to themetal material of the receptacle and mounting portion whereby thereceptacle and mounting portions are mechanically and electricallyjoined to receive and bear the stresses of insertion and withdrawal ofthe terminal and flexure of the forward spring portion in use.

References Cited by the Examiner UNITED STATES PATENTS 1,575,656 3/1926Stratford et al 339276 1,920,791 8/1933 Hogan 29470.5 2,405,111 8/1946Carlson et al 339-276 X 3,100,330 8/1963 Rice et a1 29502 X 3,140,1417/1964 Nava 339256 3,189,868 6/1965 Hatfield 339217 X FOREIGN PATENTS643,627 9/ 1950 Great Britain.

EDWARD C. ALLEN, Primary Examiner. P. A. CLIFFORD, Assistant Examiner,

1. AN ELECTRICAL CONTACT ASSEMBLY INCLUDING A BARREL PORTION AND ACONTACT PORTION INTEGRAL WITH SAID BARREL PORTION, THE SAID BARREL ANDCONTACT PORTIONS BEING OF RELATIVELY THIN FLAT METAL STOCK OF THE TYPEADAPTED FOR EASE OF STAMPING AND FORMING WITH THE CONTACT PORTION HAVINGSPRING CHARACTERISTICS, A CONTACT RECEPTACLE OF RELATIVELY HEAVY METALSTOCK SECURED IN SAID BARREL PORTION AND ADAPTED TO RECEIVE A CONTACTMEMBER INSERTED THEREIN, THE RECEPTACLE HAVING ON A PORTION OF THE OUTERSURFACE A THIN LAYER OF CONDUCTIVE MATERIAL TO ELECTRICALLY CONNECT THERECEPTACLE TO THE BARREL PORTION, THE RECEPTACLE FURTHER HAVING A RECESSAND BEING SECURED IN SAID BARREL PORTION AND ELECTRICALLY CONNECTEDTHERETO BY AT LEAST ONE INDENTATION OF THE OUTER SURFACE OF SAID BARRELPORTION FORCED INTO THE RECESS OF THE SAID RECEPTACLE.